It shouldn't be too long if you play a lot, it took me 255 battles to start from a elite IS-2 to the IS-4. I think if you use premium it should take you around 2 weeks of play, so yes it is possible. Good luck and have fun !

It took me about 350 games or so, the grind for the BL9 is the worst part of it, once you get the big gun is3 is awesome!

Wow! I have 126 battles and need about 43.5k XP more to go for the IS-4. My tip: The upgraded turret is not a waste, it's a necessity if you don't want to use tons of Gold to transfer XP from Elite tanks.